You are a circular reference.

yes there will be different for each and every ic/ component even it is same batch. but there are upper and lower control limit. let's say 1kohm 1%, it can be any value in the range of 990ohm to 1010ohm, it won't different very much.

that is resistor lor you even got 0.01% tol if you pay for it..

you think normal grade battery can get 1% tolerance? des why when making battery pack, if need high quality, you need to match each cell characteristic to the whole pack so that they can charge and discharge evenly. it's called battery matching or battery balancing.

something for you to visualize what goes on in a battery pack.

Different states of charge in a battery pack. Cell 5 has lower capacity

This post has been edited by ar188: Aug 13 2013, 09:50 PM

Greetings,

I was wondering if someone can give me a peace of mind because I recently bought a PINENG PN-910S (The one where the battery is shown in percentage ) and i verified the product to be genuine in pineng.cn. But the information at the back of the power bank is written in CHINESE instead of ENGLISH! Did I get conned?

hey bro, can you further explain of that picture? what is mean by cell 5 has lower capacity?
those battery are in series or parallel or ?

i know that battery balancing is needed for battery connected in series, for example:

all info written in Chinese ? may be newer version is like that.
older version all in English, then newer a bit is 移动电源 4 Chinese word.

seems like checking more on these issue, Li based rechargable ones have ability to balance on it's own better in parallel mode.. perhaps in battey powerbank parallel configuration it's not so much an issue compared to Ni-Cd or Ni-MH

YUP! I have those four Chinese char on the back of my pineng and other chinese char. Oh and I dont have the triangle symbol with "!" symbol in it too.

hi all powerbank sifu here, any recommend brand for powerbank? planning to get 1 but no idea which brand to go .

Sanyo / Sony.
The rated capacity might be disappointing for the price, but worth for the quality (has protections).

This post has been edited by kingkingyyk: Aug 20 2013, 07:19 PM

anyone got use tech titan powerbank b4? how is it?

i think u got it wrong with ur calculation,...

4.93VX0.94A=4.6342Watt , not watt hours,... = power

4.6342Watt x 7.33 hours = 34 watt hours...= actual energy used

rated energy suppose to be:
5V x 11200mAh = 56 watt hours (how come u use 3.7V when the actual output is 5V ??)

so the efficiency shud be only 34/56= 60.71 % instead of 82%

This is interesting. I believe it's coz the battery is 3.7V and the capacity of each cell is 2600 or 2800 mah. When added in parallel, the voltage is the same but the capacity gets summed. 11200 = 2800x4@3.7V

So I think TS is correct. Marketers will always take the highest number they can spin.

ok, this amount of instantaneous power (4.6342Watt) operate for 7.33 hours, so we get about 34 watt hours.

5V is after conversion that 's i can't take that value. The battery in 3.7V with 11200mAh capacity (4X2800) so total of 41.44Wh is supplied to the converter circuit.

input 3.7V/11200mAh ---- conversion ---- output 5V/8288mAh (ideal case)

efficiency => output power/input power

TS,

I wonder if this will help since people are confused by3.7V or 5V.

This is from some sellers who sell Pineng powerbanks, and I guess this is literature written by Pineng.

I can read it with some comprehension, but the main thing is that there is conversion loss, and the conversion factor of around 70% is reasonable.




This post has been edited by joytest: Aug 25 2013, 11:52 PM

Hi,I wanna ask,can I reuse the battery from dead laptop?
how do I test each of it if it is still in good condition?

also.
I have a Vcharge powerbank 5200mAh and it charges my 1600mah phone 1.5 times which means about 2400mAh is dissipated as charging energy on my phone.
my phone also heats up from the prolonged charging.
I want to crack it and open it up but I have already given it to my dad.
I wonder if I can open old laptop batteries,find the good ones and transplant it in cheap powerbanks.

You can try...I charged mine up then opened it up and tested each cell with a voltmeter. 2 were at 3.6V and the other 2 were around 2.5V.

I don't see a reason why it can't be repurposed into powerbanks, but it can be tough to remove the weld tabs on batteries, as they are electro-welded on the battery.

ya. I not sure whether it is written by Pineng or not. Other powerbank seller also use this to explain.
it stated 90% conversion but normally is lower than 90%

someone suggested to check for the internal resistance.
i used to check for the internal but i can't figure out whether it is good or bad battery.
may be the method i used is wrong.

You can test for the capacity. Old battery will degrade resulting in lower capacity.